Programming C#

Custom Exceptions

The intrinsic exception types the CLR provides, coupled with the custom messages shown in the previous example, will often be all you need to provide extensive information to a catch block when an exception is thrown. There will be times, however, when you want to provide more extensive information or need special capabilities in your exception. It is a trivial matter to create your own custom exception class; the only restriction is that it must derive (directly or indirectly) from System.ApplicationException. Example 11-7 illustrates the creation of a custom exception.

Example 11-7. Creating a custom exception

namespace Programming_CSharp { using System; public class MyCustomException : System.ApplicationException { public MyCustomException(string message): base(message) { } } public class Test { public static void Main( ) { Test t = new Test( ); t.TestFunc( ); } // try to divide two numbers // handle possible exceptionsexceptions public void TestFunc( ) { try { Console.WriteLine("Open file here"); double a = 0; double b = 5; Console.WriteLine ("{0} / {1} = {2}", a, b, DoDivide(a,b)); Console.WriteLine ( "This line may or may not print"); } // most derived exception type first catch (System.DivideByZeroException e) { Console.WriteLine( "\nDivideByZeroException! Msg: {0}", e.Message); Console.WriteLine( "\nHelpLink: {0}\n", e.HelpLink); } catch (MyCustomException e) { Console.WriteLine( "\nMyCustomException! Msg: {0}", e.Message); Console.WriteLine( "\nHelpLink: ...